How would HUD even work since your eyes need to focus on elements between far and close? Would you need to focus on the HUD? Does glasses work the same way? Could some nerd with glasses explain how do you focus on things?

I don't focus on the glasses lens, I focus on whatever object I'm looking at, the light reflected from which is modified by the structure of the lens.

HUD I don't know about, but can tell you, focusing on something an inch in infront of your eye is near impossible, so whatever a HUD does it must project like the image is at a distance. Probably works great for people with good eyesight already, but us aging geeks may require some adjustment as the old eyes don't want to focus up close like they once did.

Typically, the image project into the HUD is "Focused" optically at (or close to) "Infinity". Try asking the US Air Force how that works out for them (rather well, actually), as they've been using it in fighter planes for decades now.

Presumably that would require curved lenses (parabolic) reflecting the actual image to the wearer, like they use in those "holo sights" for firearms. Not impossible obviously, but not something from a standard ski goggle either.

Obviously focusing on a nearby object would be something of an issue though.

At the moment, technology has great difficulty tracking the position of the human iris unobtrusively. Given the amount of detail that would be required to watch an eye for the minute deflections and ocular muscle movements that determine the current lens' focal length, along with the necessary personal ocular detail necessary to accurately determine the current positional-space focus point of that eye, while taking into account astigmatism, hyperopia, presbyopia and myopia, such a task is currently beyond t

A heads up display allows you to look straight ahead without adjusting your focal point or moving your eye. This doesn't look as though the image is projected onto the surface of the googles. the user must make an effort to view information, it is not overlayed with the normal field of view. It's just a mini-display tucked into the corner of diving googles.

A HUD is literally a Heads Up Display, which this certainly is. Projected overlay within normal field of view is an implementation of HUD, but not its defining characteristic. In this type of application, both implementations are attached to the head rendering the inferred head position of HUD a bit moot.

Skiing is already kind of dangerous, and has lots of opportunities to run into things and people.

I'm not sure embedding a display that can distract you is necessarily a great idea...

A pure HUD overlay over the whole view that was primarily about warning you of collisions might be useful though. Especially indicators of things to the side just out of your FOV, or terrain radar warning you of ripples in the terrain you could not see because of flat light or snow.

Driving is dangerous too, yet every car comes with a vast array of readouts and inputs.

Not as dangerous: the view ahead of you is clear, the other displays are out of the way and (most importantly) not impeding peripheral vision.

I would also argue that most people skiing have much less control ability than they do in a car to react to sudden peril. Hitting brakes or steering is very easy; braking/turning sharply on uneven terrain is difficult on skis or a snowboard.

I'm not sure embedding a display that can distract you is necessarily a great idea...

It is just as distracting as the edge of your goggle frame, your hand as it moves into view, the hot skier chick who skied by.
How distracting is your speedometer when you are driving? That is about how distracting the Recon device is

I'm a bike rider (Motor, not foot powered) and I can think of many uses this would be handy for when on a cruise around the country side.
The standard email/speed/weather apps would be handy. But how about adding a rear, wide-angle camera view that I could glimpse at without turning my head around.
That would be pretty useful.